package org.loneranger.sword.offer09;

import java.util.Stack;

/**
 * 用两个栈实现一个队列。队列的声明如下，请实现它的两个函数 appendTail 和 deleteHead ，分别完成在队列尾部插入整数和在队列头部删除整数的功能。
 * (若队列中没有元素，deleteHead 操作返回 -1 )
 * <p>
 * 输入：
 * ["CQueue","appendTail","deleteHead","deleteHead"]
 * [[],[3],[],[]]
 * 输出：[null,null,3,-1]
 * <p>
 * 输入：
 * ["CQueue","deleteHead","appendTail","appendTail","deleteHead","deleteHead"]
 * [[],[],[5],[2],[],[]]
 * 输出：[null,-1,null,null,5,2]
 *
 * @author LoneRanger
 * @version 1.0
 */
public class Offer09 {

	public static void main(String[] args) {
		CQueue cQueue = new CQueue();
		System.out.println(cQueue.deleteHead());
		cQueue.appendTail(1);
		cQueue.appendTail(2);
		cQueue.appendTail(3);
		System.out.println(cQueue.deleteHead());
		System.out.println(cQueue.deleteHead());
		System.out.println(cQueue.deleteHead());

	}
}

class CQueue {
	Stack<Integer> A;

	Stack<Integer> B;

	public CQueue() {
		A = new Stack<Integer>();
		B = new Stack<Integer>();
	}

	public void appendTail(int value) {
		A.push(value);
	}

	public int deleteHead() {
		if (!B.isEmpty()) {
			return B.pop();
		}
		if (A.isEmpty()) {
			return -1;
		}
		while (!A.isEmpty()) {
			B.push(A.pop());
		}
		return B.pop();
	}
}